package main

import (
	"encoding/json"
	"fmt"
	"io"
	"os"

	"driver/lexer"
	"driver/parser"
	spec "spec/grammar"
)

func runGenerate(args []string) error {
	cgram, err := readCompiledGrammar(args[0])
	if err != nil {
		return fmt.Errorf("Cannot read a compiled grammar: %w", err)
	}

	{
		b, err := lexer.GenLexer(cgram.Lexical, "main")
		if err != nil {
			return fmt.Errorf("Failed to generate a lexer: %w", err)
		}

		filePath := fmt.Sprintf("%v_lexer.go", cgram.Name)

		f, err := os.OpenFile(filePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
		if err != nil {
			return fmt.Errorf("Failed to create an output file: %v", err)
		}
		defer f.Close()

		_, err = f.Write(b)
		if err != nil {
			return fmt.Errorf("Failed to write lexer source code: %v", err)
		}
	}

	{
		b, err := parser.GenParser(cgram, "main")
		if err != nil {
			return fmt.Errorf("Failed to generate a parser: %w", err)
		}

		filePath := fmt.Sprintf("%v_parser.go", cgram.Name)

		f, err := os.OpenFile(filePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
		if err != nil {
			return fmt.Errorf("Failed to create an output file: %v", err)
		}
		defer f.Close()

		_, err = f.Write(b)
		if err != nil {
			return fmt.Errorf("Failed to write parser source code: %v", err)
		}
	}

	{
		b, err := parser.GenSemanticAction("main")
		if err != nil {
			return fmt.Errorf("Failed to generate a semantic action set: %w", err)
		}

		filePath := fmt.Sprintf("%v_semantic_action.go", cgram.Name)

		f, err := os.OpenFile(filePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
		if err != nil {
			return fmt.Errorf("Failed to create an output file: %v", err)
		}
		defer f.Close()

		_, err = f.Write(b)
		if err != nil {
			return fmt.Errorf("Failed to write semantic action source code: %v", err)
		}
	}

	return nil
}

func readCompiledGrammar(path string) (*spec.CompiledGrammar, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	data, err := io.ReadAll(f)
	if err != nil {
		return nil, err
	}
	cgram := &spec.CompiledGrammar{}
	err = json.Unmarshal(data, cgram)
	if err != nil {
		return nil, err
	}
	return cgram, nil
}